1. Field of the Invention
This invention relates to a printer device in which a printing head effects printing on a printing medium when the printing head is contacting the printing medium with a predetermined pressure force.
2. Description of the Prior Art
In electronic computers, electronic desk top calculators, cash registers, etc., there has often been employed a method of printing input or output information on a printing medium to confirm or preserve such information. The printer devices used for such printing are generally grouped into an impact system and a non-impact system.
The impact system is a system whereby type characters carried by a type carrier such as type wheel or type belt or wires arranged in a matrix form may be selected to form a letter, and then impacted against a printing medium to provide impressions thereon. By having an inked ribbon or the like interposed between the type characters and the printing medium, it is possible to employ ordinary paper as the printing medium and this leads to a low operating cost.
However, such devices are disadvantageous in that the impact imparted by the type characters to provide impressions results in the production of noises.
The non-impact system is such that a printing head capable of representing information patterns on a printing medium is urged into contact with the printing medium by a predetermined pressure force, whereby information is printed on the printing medium by thermal, electrical or electrochemical means. The non-impact system avoids the noise produced during printing, but it still suffers from some disadvantages associated with the mechanism for moving the printing head to impress a plurality of information patterns on the printing medium.
More specifically, when a letter in a line has been printed on the printing medium, the printing head must undergo a letter feed movement in preparation for printing another letter and this has heretofore been done by either one of the two methods which will be described hereinafter.
In one method, the printing head is urged into contact with the printing medium by the same pressure force both during the printing and the letter feed movement, and the letter feed occurs with the printing head under such a pressure force. Such a system leads to simplification of the mechanism for controlling the movement of the printing head and the elimination of the noises during the movement, as well. Nevertheless, if the pressure force with which the printing head must contact the printing medium during the printing is great, the friction between the moving printing head and the printing medium would result in wear to the head and/or damage of the printing medium, and this would almost preclude the use of soft materials for the printing medium. Moreover, since the printing head and the printing medium are in contact under the same pressure force, both during the movement and the printing, a large drive force is required to move the printing head and this necessitates the provision of a large motor which, in turn, results in bulkiness of the entire device.
There is still another non-impact systemf whereby the printing head during its movement is maintained out of contact with the printing medium. In such a system, the above-noted disadvantages are eliminated, but the printing head must be separated out of contact with the printing medium during each movement of the head and again brought into contact with the printing medium when the printing head has been moved to a printing position, and this causes noises, as in the impact system. Thus, the great merit of the non-impact system which is free of noise production is entirely offset.
A further disadvantage of this system is that the printing speed is reduced due to the time required, the time for separating the printing head from the printing medium when moving the former and the time required for bringing the printing head into contact with the printing head by a predetermined pressure force prior to printing.